A known inkjet head has a flow path unit formed with an ink flow path including a common ink chamber and a plurality of individual ink flow paths from the exit of the common ink chamber to a nozzle. The flow path unit has a stack structure wherein a plurality of plates are stacked on each other. Through holes formed in the plates are connected to each other, whereby an internal ink flow path is formed. An art of forming positioning holes in plates and inserting the positioning holes into positioning pins, thereby positioning the plates is known. However, in such an inkjet head, the ink flow path formed in the flow path unit is made increasingly smaller and smaller due to the demands of higher density of the nozzle and miniaturization of the inkjet head. Thus, with the dimensions of the ink flow path becoming more and more fine, the plates need to be positioned with even higher accuracy so that the through holes formed in the plates are joined precisely in a manufacturing process of the flow path unit.